The main theme of this asthma and allergic disease center application is focussed on immunoregulation and interaction between cells participating in immunologic and/or inflammatory responses. Most of the investigators involved in this work have a background well founded in immunology, have developed and/or are using in vitro models to study immunologic reactions, and are applying the new information to patients with allergic and hypersensitivity diseases. An example of how we are approaching this problem is presented in the first project in which the effect of immunotherapy in cat-induced asthmatics is being investigated. In this project, several facets of immune function as well as the clinical benefit derived from immunotherapy is being evaluated.